package co.kensure.weixin;
 
import java.security.AlgorithmParameters;
import java.security.Security;
import java.util.Arrays;

import javax.crypto.Cipher;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;

import org.bouncycastle.jce.provider.BouncyCastleProvider;

import com.alibaba.fastjson.JSONObject;
import com.sun.org.apache.xerces.internal.impl.dv.util.Base64;
 
/**
 * @author ljh
 */
public class WXUtils {
    public static JSONObject getUserInfo(String encryptedData, String sessionKey, String iv){
        // 被加密的数据
        byte[] dataByte = Base64.decode(encryptedData);
        // 加密秘钥
        byte[] keyByte = Base64.decode(sessionKey);
        // 偏移量
        byte[] ivByte = Base64.decode(iv);
 
        try {
            // 如果密钥不足16位，那么就补足.  这个if 中的内容很重要
            int base = 16;
            if (keyByte.length % base != 0) {
                int groups = keyByte.length / base + (keyByte.length % base != 0 ? 1 : 0);
                byte[] temp = new byte[groups * base];
                Arrays.fill(temp, (byte) 0);
                System.arraycopy(keyByte, 0, temp, 0, keyByte.length);
                keyByte = temp;
            }
            // 初始化
            Security.addProvider(new BouncyCastleProvider());
            Cipher cipher = Cipher.getInstance("AES/CBC/PKCS7Padding","BC");
            SecretKeySpec spec = new SecretKeySpec(keyByte, "AES");
            AlgorithmParameters parameters = AlgorithmParameters.getInstance("AES");
            parameters.init(new IvParameterSpec(ivByte));
            cipher.init(Cipher.DECRYPT_MODE, spec, parameters);// 初始化
            byte[] resultByte = cipher.doFinal(dataByte);
            if (null != resultByte && resultByte.length > 0) {
                String result = new String(resultByte, "UTF-8");
                return JSONObject.parseObject(result);
            }
        } catch (Exception e) {
           	throw new RuntimeException(e);
        }
        return null;
    }
    
    public static void main(String[] args) throws Exception{
 	   String appId = "wxdf45f1f8e71cb740";
 	   String encryptedData = "bGx20RwtP+2CsDTluJWzDwU4WR+4HFAaj2YtmGq4tAgdY98E1jAX4NCNu3SxRNV0r5EsnCry5qAJzdCgpy+fu5pIl2oTVdJ2+3NjKyEsIHrrJGLiv7mwV643wUxvyx1iSPsV38YrK4c8S7EfjfN09xwdiPnxZ0OFDNcjL63AGxYPkJWJUAfHa6CsyFwLmmfyLhy9BK7IGDw9rTKxkWtCRA==";
 	   String sessionKey = "CG4iDsT7zutVkI/+zZIY5g==";
 	   String iv = "tG0BBGSIAUb6pxzZeE5aTA==";
        System.out.println(getUserInfo(encryptedData, sessionKey, iv));
     }
 
}
	
	